Experimental Research On Down Hole Deep Compaction Pile In Collapsible Loess Ground

The down hole deep compaction method has its unique advantage in the treatment of collapsible loess foundation. The foundation treatment method in the area of collapsible loess has been applied more and more in the engineering construction and has brought huge economic and social benefits. The treatment of collapsible loess with large thickness based on this method is possible in theory, but its construction technology and practical result still remain to be tested in practice.The research in this essay is carried out on a large project in Yuzhong County in the city of Lanzhou. Through engineering tests on collapsible loess with large thickness, I have analyzed and summarized the engineering-related issues such as design parameters, engineering equipment, quality control and quality inspection. All those can provide a powerful support to the further application of this method. The research on this essay has a great importance to the construction in the collapsible loess area which is lacking in reliable bearing layer.The experiment focuses on a35m-long pile experimental area. Through pre-humidification, pile formation and water immersion test, I have analyzed the parameters, construction technology and testing technology systematically. Based on the analyses, this essay offers some practical suggestions on quality control and optimization. In the50m-long pile experimental area, the research lays emphasis on engineering technology, with construction equipment and engineering parameter also summarized. The test result shows that it can not only effectively eliminate the possibility of collapsibility of loess but also has the advantages of simplicity and flexibility.In the research, I have conducted model tests based on the similarity theory to study the impacts that hammers bring to ground treatment. In the tests, I use hammers with different angles and length diameter ratio to know the hammer factors in the treatment. Through the analyses of void ratio, coefficient of compactness and so on, I have reached the conclusion that the squeezing effects of the soil between piles will be weakened but the squeezing effects of the pile will be enhanced with the increase of the hammer angles. So this essay puts forward an optimized hammer shapes through the analysis of hammer angles. Model tests are also adopted in my research to study the reasonable spacing between piles. The study shows that the reasonable spacing is between2.5d and3d (d is the diameter of pile hole). The spacing between piles can be increased accordingly when the compact energy is enhanced.